[ClusterLabs] Antw: Re: Question on sharing data with DRDB

[Ulrich Windl]

>>> Digimer <lists at alteeve.ca> schrieb am 20.03.2019 um 17:37 in Nachricht
<37a2b613-62ce-a552-804a-df5199674b00 at alteeve.ca>:
> Note;
> 
>   Cluster filesystems are amazing if you need them, and to be avoided if
> at all possible. The overhead from the cluster locking hurts performance
> quite a lot, and adds a non-trivial layer of complexity.

Yes, that's the true challenge. It's sad that NFS might provide better
performance than a cluster filesystem will.

> 
>   I say this as someone who has used dual-primary DRBD with GFS2 for
> many years.
> 
>   To expand on why you can't use something like ext4; Non-cluster-aware
> file systems expect all changes to the backing device to go through it.
> So there's no mechanism to tell the FS on one node that blocks have
> changed because of actions on another node. Likewise, they have no
> mechanism to coordinate sane and safe access to blocks. These mechanisms
> are exactly what makes a cluster FS what it is.
> 
> digimer
> 
> On 2019-03-20 11:52 a.m., Emmanuel Gelati wrote:
>> If you need to access from both nodes, you need to use primary/primary
>> mode in drbd
>> 
>> Il giorno mer 20 mar 2019 alle ore 16:51 JCA <1.41421 at gmail.com 
>> <mailto:1.41421 at gmail.com>> ha scritto:
>> 
>>     OK, thanks. Yet another thing I was not aware of in the clustering
>>     world :-(
>> 
>>     On Wed, Mar 20, 2019 at 9:41 AM Valentin Vidic
>>     <Valentin.Vidic at carnet.hr <mailto:Valentin.Vidic at carnet.hr>> wrote:
>> 
>>         On Wed, Mar 20, 2019 at 09:36:58AM -0600, JCA wrote:
>>         >      # pcs -f fs_cfg resource create TestFS Filesystem
>>         device="/dev/drbd1"
>>         > directory="/tmp/Testing"
>>         >         fstype="ext4"
>> 
>>         ext4 can only be mounted on one node at a time. If you need to
>>         access
>>         files on both nodes at the same time than a cluster filesystem
>>         should
>>         be used (GFS2, OCFS2).
>> 
>>         -- 
>>         Valentin
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>> -- 
>>   .~.
>>   /V\
>>  //  \\
>> /(   )\
>> ^`~'^
>> 
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> 
> 
> -- 
> Digimer
> Papers and Projects: https://alteeve.com/w/ 
> "I am, somehow, less interested in the weight and convolutions of
> Einstein’s brain than in the near certainty that people of equal talent
> have lived and died in cotton fields and sweatshops." - Stephen Jay Gould
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